The invention relates to electroactive organic materials and more particularly to novel electroactive polymers and their synthesis. In particular, the invention is directed to polymers having 6,6,6-membered tricyclic moieties as pendant groups. The groups act as electron donors which, in the presence of an electron acceptor dopant, render the polymer conductive.
Electronic properties of a polymer containing an electroactive pendant group depend on electron transfer between adjacent or nearby pendant groups. Therefore the orientation, stacking and proximity of the pendant groups is a major determining factor in the success of a given polymer as an electroactive polymer. These properties, in turn, depend on the repeating unit length, spacer group length and the conformational requirements of the polymer backbone.
Polymers that contain electroactive groups as pendant groups or as a part of the polymer backbone are of considerable interest as electrode modifiers, in polymeric redox systems and in photo- and semiconductors. A number of aromatic heteropolycyclic compounds, among them phenothiazine and its derivatives, have been shown to have semiconduction, electron donation and photoconduction properties. Polymers containing phenothiazine can be used as redox polymers and semiconducting and charge transfer polymers. The benzene ring-substituted derivatives of phenothiazine are known to be effective free radical scavengers, which prevents their use as vinyl monomers. However, the N-substituted phenothiazine derivatives, such as N-vinyl and N-acrylyl phenothiazine, undergo free-radical addition polymerization with ease.
U.S. Pat. No. 4,505,841 discloses electroactive polymeric materials which are said to be soluble in various solvents. The polymers are comprised of recurring units of fused unsaturated 6,6,6-membered heterocyclic rings wherein the central ring contains the heteroatoms. Charge compensating ionic dopants are associated with the polymers. Phenothiazine polymers, in which the heteroatoms are nitrogen and sulfur, are disclosed, whereby phenothiazine repeating units are incorporated into the backbone of the polymer.
One of the problems associated with prior art conductive polymers in general is their insolubility in organic or aqueous solvents. Because of this, the polymers are very difficult to process into usable forms, such as films, etc.
Another problem of some prior art conductive polymers is that the electrical conductivity decreases over time, possibly due to oxidative effects.